The Chemical Constituents of the Organism. 19 



The large amount of phosphoric acid and the preponder- 

 ance of lime, afford us some explanation of the rapid growth 

 of bone in the young of these animals ; the large proportion 

 of potassium and sodium in the cow, and the excess of 

 potassium over sodium in the mare, are points more difficult 

 of explanation, but bear out what I have yet to show, viz., 

 the preponderance of potassium over sodium salts in the 

 excretions of the horse. 



Bunge compared the ash of a puppy with the milk of the 

 mother, and the milk with the blood. It is remarkable 

 how closely the composition of the puppy's system agreed 

 with the salts it was receiving with the milk, though when 

 the ash of the milk was compared with the ash of the blood 

 of the mother, the greatest diversity in composition was 

 apparent. This observer showed that the ash of the milk 

 contained more potassium and less sodium than the ash 

 found in the body of the young animal. We may also see 

 that in cow's and mare's milk the potassium exceeds the 

 sodium, and Bunge explains it by saying that as the animal 

 grows it becomes richer in potassium and poorer in sodium 

 salts, depending upon the relative increase in the muscular 

 structure which is rich in potassium, and the relative 

 decrease of the cartilaginous material which is rich in 

 sodium. 



In referring to Bunge's analysis of the cow's and mare's 

 milk, one is struck by the small proportion of chlorine in 

 the latter ; I cannot offer any explanation why the calf 

 requires so much more chlorine and sodium than the foal. 

 The chlorides in the body are required not only for building 

 up tissues, but in the production of secretions, and some 

 considerable difference must exist in the constitution of the 

 calf and foal to admit of such a difference in the amount of 

 chlorine required. 



Turning to the adult, we find that vegetable food furnishes 

 considerably more potassium than sodium salts to the 

 system, and Bunge's views about the muscle growth apply 

 here also. 



Sodium and Potassium. — Owing to the poorness of vege- 



2—2 



